1. Field of the Invention
The present invention relates to a non-ester type epoxy resin containing no ester bonds a resin composition containing the resin, and use of the resin composition.
2. Description of the Related Art
In recent years, rapid curing of epoxy resins at low temperatures has been desired. For instance, photo-cationic curing using a photo acid generator has been studied. In general, a glycidyl ether type epoxy resin has a low reaction rate and an epoxy group thereof also has low reactivity. Thus, there arises a problem in that the glycidyl ether type epoxy resin does not provide a cured product having sufficient characteristics. For solving such a problem, for example, JP 11-263827 A discloses the study of a chlorine-free alicyclic epoxy resin having excellent cationic curability. In JP 11-263827 A, however, the alicyclic epoxy resin used contains ester bonds, and a cationic curing rate is not sufficient. Furthermore, ester bonds are cleaved by a cationic component generated in curing to generate carboxylic acids, leading to large problems of an increase in water absorption of a cured product, a decrease in a glass-transition temperature (Tg) thereof, and so on.
Furthermore, an epoxy resin to be industrially used is generally obtained from a reaction between a phenol compound and epichlorohydrin (ECH). A glycidyl compound generated in a production process contains chemically-bonded chlorine in a content of several percent depending on the process conditions. However, a chlorine-free epoxy resin has been needed in terms of environmental and safety problems, for example. In the use thereof for electronic materials, in particular, hydrolytic chlorine atoms in an epoxy resin have been regarded as a problem because these chlorine atoms are ionized to cause lowering of reliability such as corrosion of wiring or the like and decrease in insulating property. Therefore, various studies have been made to decrease a content of hydrolytic chlorine atoms in the epoxy resin to free the chlorine atoms. In spite of such efforts, the total chlorine content of the resulting epoxy resin is about several hundreds ppm. Additional purification is needed for further reducing the chlorine content, resulting in a very expensive product.
It is an object of the present invention to provide a non-ester type epoxy resin having a low hydrolytic chlorine content and containing no ester bonds that are easily hydrolyzed. According to the present invention, the non-ester type epoxy resin can be realized by means which can be easily changed through adjustment of process parameters and selection of appropriate starting compounds. In other words, the present invention is characterized in that a non-ester type epoxy resin containing no hydrolytic chlorine atoms can be readily provided at low cost.